Loss analysis and design optimization of a small scale mixed-flow pump turbine using the orthogonal method

为了研究各部件对小型混流式水泵水轮机水泵工况和水轮机工况下水力性能的影响,对一小型水泵水轮机进行不同流量下的全流道数值模拟,针对两工况下总压损失集中的叶轮进行正交设计优化。应用L9（3⁴）正交表,选取4个叶轮关键设计参数,以水泵工况扬程偏离率、效率和水轮机工况效率作为目标,进行4因素3水平的正交设计,并通过全流道数值模拟方法和极差分析方法进行选优。结果表明叶片出口直径对泵和水轮机工况性能影响最大,优化后水泵设计工况效率提高了1.06%,水轮机设计工况效率提高1.62%,其相应最优工况点因包角增加而向小流量工况移动。     

涡流发生器对潮流能水轮机叶片流动分离特性影响研究

当来流速度过大或在大攻角来流工况下,潮流能水轮机叶片边界层会发生流动分离,导致获能效率降低,甚至会使叶片发生失速破坏。针对上述问题,该文将涡流发生器（VGs）理论与水轮机叶片设计相结合,开展VGs对潮流能水轮机叶片流动分离现象的抑制机理研究。以NACA63418翼型设计的潮流能水轮机叶片为研究对象,分别建立带和不带VGs的叶片三维模型,应用CFD方法研究VGs对潮流能水轮机叶片的流动分离特性影响。结果表明：水轮机叶片流动分离主要发生在吸力侧表面叶根部分,随着流速的增大会沿叶根向叶尖径向扩展;VGs能有效减小水轮机叶片吸力侧表面分离区域,抑制流动分离现象发生;在该研究中,安装VGs后水轮机叶片整体获能性能提升明显,获能系数增加0.5%~5.0%,且能增加潮流能水轮机运行稳定性。     

新型简易太阳水泵的性能分析和试验

本文对BT-SⅡ型太阳水泵的性能进行了分析和计算,在理论上确定了最佳运行工况。运行表明,该泵操作容易,运行可靠,具有自起能力,试验结果与理论分析一致。本文还对典型试验结果进行了(火用)分析。首先是提高集热器(火用)效率,其次是减小冷凝器(火用)损失和隔膜泵热能与机械能损失,将使系统的性能得到改善。     

叶片前缘偏转对H型垂直轴水轮机性能的影响

为提高传统直叶片升力型（H型）垂直轴水轮机的获能效率,提出一种带前缘可偏转叶片的新型垂直轴水轮机,利用计算流体力学（CFD）方法,结合重叠网格和动网格技术对这种新型垂直轴水轮机叶轮的水动力性能进行系统的数值模拟计算,分析不同叶尖速比下带前缘偏转叶片的垂直轴水轮机绕流流场,从而探究前缘偏转角度和偏转长度对这种水轮机动力性能和获能效率的影响规律。结果表明,根据叶片旋转到不同位置时实施前缘偏转可改变来流攻角从而减缓或抑制叶片吸力面的流动分离,有效改善其动态失速特性,进而使H型垂直轴水轮机的水动力性能和获能效率得到明显提升。研究发现,低叶尖速比下这种改善效果最为显著,可拓宽H型垂直轴水轮机高效运行的工作范围。     

跨临界CO2制冷循环火用分析

基于热力学第二定律,对跨临界CO2制冷循环过程的损失及火用效率进行理论分析,发现节流过程火用损失最大,循环火用效率为25%。提高蒸发温度和降低冷却终了温度是提高循环火用效率的有效途径;升高冷却压力,可以降低节流过程火用损失,但是对循环火用效率影响不大。     

水泵水轮机泵工况下内部空化特性分析

为研究空化条件下水泵水轮机泵工况的内部空化特性,基于ANSYS CFX(有限元分析)软件采用k-ε湍流模型、均质多相模型和Rayleigh-Plesset方程,对某抽水蓄能电站模型机进行了全流道非定常空化流动数值计算。根据模拟结果预测了水泵水轮机泵工况工作无空化时的能量特性和空化发生时的空化性能,并与试验数据对比。结果表明:流场数值计算成功地捕获到了空化发生、发展及空间演变过程;随着空化数的变化,空泡在叶片背面进口附近产生,然后沿着流线向叶轮出口扩散,并随着流道过流面积的增大向叶片工作面扩展,直接影响叶片上的压力分布和叶片中间流线上叶片载荷分布;在空化严重时,会造成叶轮流道内流动紊乱和严重堵塞,导致效率的大幅下降,对机组安全稳定运行非常不利。     

基于超声波法与蜗壳差压法测流的可逆式水泵水轮机效率测试软件的开发及应用

为解决抽水蓄能机组水泵工况下的效率测试问题,研制开发了针对水泵水轮机的效率特性测试软件。该软件系统综合考虑了水轮机工况和水泵工况的效率测试,采用超声波测流法或蜗壳差压测流法完成水泵水轮机的绝对效率或相对效率试验。软件系统通过RS232/485串口和采集仪实时采集和传输各试验参数,并可对采集数据进行分析计算和图形化显示,方便地获得水泵水轮机效率特性。现场应用表明,该软件系统设计合理、运行稳定、数据计算结果准确,具有一定的推广价值。     

福建周宁抽水蓄能电站水泵水轮机模型试验分析

本文介绍了福建周宁抽水蓄能电站水泵水轮机模型试验的过程,分析了模型试验的结果.试验结果表明,模型水泵水轮机的效率、流量、压力脉动等各参数均符合采购合同的规定,符合电站安全运行的要求.以模型试验的数据为基础,可计算出原型性能,为原型的设计及制造、安装及运行提供了可靠的依据.     

水泵水轮机调相运行水环内部流动分析

水泵水轮机调相运行是抽水蓄能机组转换工况的一个重要过程,在泵工况下压水起动过程中,转轮腔体内注入压缩空气以降低泵启动所需功率。以中比转速水泵水轮机的模型为例,基于RNGκ-ε湍流模型,采用VOF多相流模型对水泵水轮机运行在泵工况压水起动阶段的水环现象进行非定常流动分析,探讨水环现象下不同冷却水流量对无叶区内部流动的影响。结果表明,空气与水在无叶区内形成明显的交界面,构成一定厚度的水环,该水环可有效阻止空气从转轮腔体内泄露至蜗壳内,起到对空气的密封作用。同时在不同冷却水流量下,无叶区内的压力脉动均呈动静干涉现象,其主频为叶片通过频率。     

导叶不同开度下抽水蓄能机组水轮机工况内流特性分析

为了解抽蓄机组水轮机工况下活动导叶不同开度下的内流特性,以某抽水蓄能电站水泵水轮机为研究对象,基于SST k-ω湍流模型,进行活动导叶不同开度下全流道三维非定常数值模拟和分析,探讨活动导叶开度对过流部件内部流场的影响.结果表明:随着导叶开度的增加,水泵水轮机的流量增大,转轮力矩增大但增幅降低,效率先增大后降低.蜗壳整体上的压力沿周向分布比较均匀,从蜗壳进口到蜗壳出口均匀降低,水力损失较小;固定导叶形状及安放角与活动导叶搭配影响较大,小开度和大开度工况下活动导叶和固定导叶进口处水力损失大;压力变化线与进出口是否平行影响转轮内部流态,中开度转轮叶片做功最好;小开度工况下易产生偏心涡带,降低机组效率,不利于尾水管能量的回收,中开度工况下尾水管流态最好.研究结论对抽水蓄能机组运行提供了理论参考.     

Second law analysis of reverse osmosis desalination plants: An alternative design using pressure retarded osmosis

A second law analysis of a reverse osmosis desalination plant is carried out using reliable seawater exergy formulation instead of a common model in literature that represents seawater as an ideal mixture of liquid water and solid sodium chloride. The analysis is performed using reverse osmosis desalination plant data and compared with results previously published using the ideal mixture model. It is demonstrated that the previous model has serious shortcomings, particularly with regard to calculation of the seawater flow exergy, the minimum work of separation, and the second law efficiency. The most up-to-date thermodynamic properties of seawater, as needed to conduct an exergy analysis, are given as correlations in this paper. From this new analysis, it is found that the studied reverse osmosis desalination plant has very low second law efficiency (<2%) even when using the available energy recovery systems. Therefore, an energy recovery system is proposed using the (PRO) pressure retarded osmotic method. The proposed alternative design has a second law efficiency of 20%, and the input power is reduced by 38% relative to original reverse osmosis system.     

Photovoltaic thermal collectors: Reverse osmosis desalination system as an application

Solar energy presents one of the frequent used energy resources to desalinate water especially with reverse osmosis desalination process. Photovoltaic thermal collector (PV/T) is a hybrid generator which converts solar radiation into useful electric and thermal energies simultaneously. This paper gathers all PV/T submodels and reverse osmosis desalination model in order to form a unique dynamic model that reveals PVT based reverse osmosis desalination interactions. As the system is a multi-input/output/output system, a state space model based on energy balance equations is developed in order to analyze and assess the parameters behaviors and correlations of the system constituents. The model simulation is performed using LabVIEW software. The simulation reveals the influence of heating feed water on the process efficiency and the afforded energetic gain by the coolant fluid circulation.     

节水新技术在长庆石化公司的应用

长庆石化先后建设两套70m3/h初级再生水深度处理回用装置、一套60m3/h反渗透浓水回用装置和一套80m3/h凝结水除油除铁装置,采用的超滤、反渗透、陶瓷超滤等新技术,具有装置分离效果好、占地面积小、操作简单、安全环保等优点,应用"超滤+反渗透"双膜系统,其污水水质逐步改善,浊度明显下降,由过去的平均25NTU,下降为8NTU,实现了废水回用,有利于循环水系统的长周期运行,特别在减少换热设备腐蚀和黏泥生成,延长换热设备寿命、提高换热效率上有突出作用;浓水反渗透及二级除盐水系统的建立,实现了废水高等级回用,在同等工况下,2008年与2007年相比,除盐水消耗量平均减少1663t/d;应用无机陶瓷滤膜技术,又在实现废水高等级回用的同时,将其热能一并回收利用,真正达到高水高用的目的。几套装置合计投资为991万元,新增收益合计为680.2万元,投资收益比为0.69,投资回收期在2a以内。应用上述工艺处理后的废水,分别用作循环水系统、空冷装置和工业锅炉的补充水,吨油耗水从2002年的1.08t/t,下降为2010年的0.58t/t。     

膜分离技术处理丙烯腈装置含氰废水研究

利用膜分离技术处理含氰废水具有投资少、不污染环境的特点,市场应用前景广阔。开展了膜分离技术处理丙烯腈含氰废水实验研究。该实验采用超滤和反渗透膜组合分离工艺,目的是考察反渗透膜型号和种类,获得抗污染膜牌号;摸索去除CN-最佳工艺参数,实现COD、CN-含量等指标达标。实验结果显示：①采用超滤和反渗透膜组合技术可有效分离丙烯腈含氰废水中的有机组分,在此技术路线上可以开展工业化装置研究;②采用两级陶氏反渗透膜,COD去除率可达83.31%、CN-去除率可达51.08%,合格率可达100%;③可用NaOH调节含氰废水的pH值,pH值控制在9.5～10.5之间,可有效提高CN-去除率。采用膜分离技术处理丙烯腈含氰废水,年节约排污费近60万元。     

脱硫废水零排放技术在清远电厂中的应用探讨

结合国华清远项目的建厂条件,针对对脱硫废水零排放的蒸馏法、反渗透法和正渗透法三种主要处理工艺,通过对其技术性能和经济成本的综合比较,提出了将反渗透浓缩结晶工艺作为电厂脱硫废水处理工艺首选方案的建议,为电厂下阶段零排放处理工艺选择提供了重要技术支持和参考。     

On the feasibility of community-scale photovoltaic-powered reverse osmosis desalination systems for remote locations

This paper presents a generalized methodology to evaluate the feasibility of photovoltaic-powered reverse osmosis (PVRO) systems for small, remote communities in challenging environments. The economic feasibility is determined by comparing the cost of water from a photovoltaic reverse osmosis system with the cost of water obtained using conventional diesel-powered reverse osmosis. For PVRO systems, the feasibility is a function of location due to variation in solar resource, water type, system demand and local governmental policies. A series of sample cases were analyzed to demonstrate the method. Analysis for community-scale seawater reverse osmosis systems was carried out for various locations using Geographic Information System (GIS) data. A site-specific analysis has been completed for seawater and brackish water reverse osmosis systems. It was found that photovoltaic-powered reverse osmosis is feasible for the majority of remote locations with a large solar resource.     

Exact solution to mass transfer in Berman flow: Application to concentration polarization combined with osmosis in crossflow membrane filtration

Concentration polarization affects numerous systems of membrane separation, and combined with osmosis, it can cause substantial reductions in permeation. We establish an exact solution to the conservation law of a solute advected by Berman flow. This flow is characteristic of reverse osmosis or nanofiltration. The resulting concentration polarization is then combined with the osmosis (counter-) effect. For large Péclet number of permeation, it yields a rigorous support to the semi-empirical “film” model, and accounts for the limit flux phenomenon. The main results are summarized in a simple diagram that relates three different Péclet numbers, and show that polarization combined with osmosis can withstand operating pressure almost totally.     

The cost of water from an autonomous wave-powered desalination plant

A techno-economic model of an autonomous wave-powered desalination plant is developed and indicates that fresh water can be produced for as little as £0.45/m³. The advantages of an autonomous wave-powered desalination plant are also discussed indicating that the real value of the system is enhanced due to its flexibility for deployment and reduced environmental impact. The modelled plant consists of the Oyster wave energy converter, conventional reverse osmosis membranes and a pressure exchanger–intensifier for energy recovery. A time-domain model of the plant is produced using wave-tank experimentation to calibrate the model of Oyster, manufacturer's data for the model of the reverse osmosis membranes and a hydraulic model of the pressure exchanger–intensifier. The economic model of the plant uses best-estimate cost data which are reduced to annualised costs to facilitate the calculation of the cost of water. Finally, the barriers to the deployment of this technology are discussed, but they are not considered insurmountable.     

吸附-扩散模型一级近似式及其应用

对吸附-扩散模型进行数学简化,得到一级近似式,并对一级近似式与溶解-扩散模型的相互关系进行了研究。利用吸附-扩散模型一级近似式对KCl溶液反渗透过程进行模拟,结果表明模型近似式能较好地模拟反渗透脱盐过程。     

反渗透技术在压风系统中的应用

叙述了反渗透净水的原理及反渗透净水设备的应用。指出,反渗透技术的应用可减少了冷却水的用量,又不用再进行压风系统的清洗。